1. Field of the Invention
The present invention relates generally to magnetic heads and their fabrication, and more specifically to manufacture of pole pieces for write heads which contain elements made of CoFe.
2. Description of the Prior Art
A computer disk drive stores and retrieves data by positioning a magnetic read/write head over a rotating magnetic data storage disk. The head, or heads, which are typically arranged in stacks, read from or write data to concentric data tracks defined on surface of the disks which are also typically arranged in stacks. The heads are included in structures called “sliders” into which the read/write sensors are imbedded during fabrication. The goal in recent years is to increase the amount of data that can be stored on each hard disk. If data tracks can be made narrower, more tracks will fit on a disk surface, and more data can be stored on a given disk. The width of the tracks depends on the width of the poles in read/write heads used, and in recent years, track widths have decreased as the size of read/write heads have become progressively smaller. This decrease in track width has allowed for dramatic increases in the recording density and volume of data storage of disks.
The type of head for writing data is generally configured with two poles separated by a gap layer of non-magnetic material. These are generally referred to as the first pole or P1 and the second pole P2, with a non-magnetic gap layer between them. In order to maximize the density of information on the disk, tracks and the heads that write them are reduced in size further and further. This requires that the magnetic flux which is used to write the data must be channeled and concentrated to smaller and smaller areas. It is now typical that magnetic flux be channeled from a relatively wide structure though a kind of funnel or yoke and concentrated through the very narrow P1 and P2 poles. Although this has worked well in the past, a limit is being approached as far as the ability of the pole tip material to conduct very-high densities of magnetic flux. A quantity known as Bs is a measure of the saturation point of a material for magnetic flux density. The most commonly used material for fabrication of the P1 and P2 poles has been NiFe, which has a Bs of 1.8 T Recently another material CoFe has been explored for use in this application, and CoFe has a higher magnetic moment saturation value of 2.4 T. The implication of this is that poles can be made much narrower with CoFe than with NiFe without encountering the Bs saturation limit.
However, CoFe is more chemically active than NiFe, and chemicals used in manufacturing processes of these magnetic heads can end up damaging the CoFe components, especially during the Chemical Mechanical Polishing (CMP) stages. FIGS. 5–7 show exemplary heads having elements made of CoFe, which have been damaged by pits produced by chemical action during the CMP process, using standard methods and materials.
Thus there is a need for a method and materials for fabricating magnetic heads having elements of CoFe without the damage to components that typically happens using existing CMP processing.